My defintion said nothing about "social norms". "Established standards of behaviour". They aren't the same thing as "social norms".
Well, I would use the terms interchangeably, but you are saying this does not accurately reflect your view on the term, so I'll work with that. What, then is "established standard of behavior?" Who or what is establishing it, if not society?
If you're going to argue that every single individual establishes it for themselves, then you are defining morality as a necessarily subjective thing, and that would be a pretty lame argument.
I'm not going to address the rest of your post just now, because I'm planning my own objective morality thread (because there's always room for more, right?), and it's going to be a very long one that focuses on some of the misunderstandings that are repeatedly cropping up. For now, I'll leave you with this.
I see morality as a thing that is distinct from any other thing that we would define as subjective. Let's take, for example, your favorite band. This is obviously subjective. Is there anything I could do to convince you that you do not like your favorite band? Of course not. That would be ridiculous. But what about morality? Whereas you may feel that some given moral issue is good, what if I could convince you that this thing actually causes great suffering? Being the level-headed individual you are, wouldn't you change your mind on the issue, and come to the conclusion that this thing is actually not good? This is why I define morally bad things as those which cause suffering, and reduce well-being, and morally good things are their opposite.